Snap action switch



Nov. 14, 1950 L. M. PERSONS SNAP ACTION SWITCH Filed May 15, 1947 INVENTOR3 LAWRENCE M. PERSONS ATTORNEYS.

' tion switch.

Patented Nov. 14, 1950 SNAP ACTION SWITCH Lawrence M. Persons, Ohesterfield, Mo., assignor to McQuay-Norris Manufacturing Company,

St. Louis, Mo.,

a corporation of Delaware Application May 15, 1947, Serial No. 748,222

- 1 This invention relates generally to electrical control apparatus and particularly-to a snap ac- While snap action switches have heretofore been provided in a variety of forms, the devices of the character heretofore known have not only been diflicult and tedious to manufacture, but have required a substantial movement of an actuating member in order to initiate the movement of the switch parts from one position to another.

The object of the present invention, generally stated, is to provide a snap action switch, which is not only economical to manufacture and easy to assemble, but which is actuated from one position to another in response to very-slight movements of an actuating member.

Other objects will become apparent to those skilled in the art when the following description is read in connection with the. accompanying drawings, in which:

Figure l is a view in side elevation (the enclosing case being shown in section) of a snap action switch constructed in accordance with the present invention;

Figure 2 is a sectional view taken along line 2-2 of Figure 1; and

Figures 3, 4, 5, and 6 are a series of diagrammatic views illustrating the several positions of the cooperating parts of the switch shown in Figure 1.

In accordance with the present invention, a snap action or toggle type switch is produced and the contact member maintained in position solely through the oflice of an over-center spring, whose force is exerted in a direction such as to maintain the contact member seated upon a knife-edge pivot. Consequently, the contact member may be readily dismounted from the organization by relief of the spring tension thereon. A further important feature of the invention is to provide in the organization of contact members and actuating members an arrange.- ment whereby the contact member is positively moved upon failure of the impositive spring connections to'move the same, as sometimes results when the contacts stick.

Referring now to the drawings for an illustrative embodiment of the invention, a contact member I is provided with a knife;edge bearing 2 seated upon a bracket 3 carried by an'insulation base 4.

In the form shown, .the contact member I is provided with a pair of movable bridging contacts 5 arranged for selective engagement with a set of stationar contacts 8 or a set of stationary 8 Claims. 01. 200 83) 2 contacts I, in accordance with the of.

In order to hold the contact member I seated upon the bracket 3, a thrust link 8 having a tongue 9 projecting through a lip III of the contact member I is provided. The other end of the position therelink 8 is engaged by a leaf spring I'I stressedso a as to urge the contact member I continuously in the direction which maintains the knife-edge 2 seated upon the bracket 3. The connection between the link 8 and the spring II is similar to the connection between the link and the contact member I consisting of a tongue I2 extending through an orifice inthe leaf sp i t II.

The spring I I is mounted for movement in a vertical direction, as shown in Figure 1. In the embodiment shown, the mounting for the spring II consists of a piece of insulating material I 26 t connected to the extremity of a lever I3, which latter is pivoted on a shaft l4. Within the confines of the adjunct structure, the spring II is, therefore, movable about shaft It as an axis.

The actuating force to initiate movement of lever I3 and spring II about axi I4 is applied, in the embodiment illustrated, through an operating lever I5 pivoted on shaft I 6.

The end of lever I5 most remote from its point of pivot is arranged to engage a boss H on lever I3 closely adjacent the pivot-axis of the latter. Intermediate the ends of operating lever I5, a pressure member I8 is arranged to bear. In the embodiment illustrated, the pressure member I8 is associated with a bellows'and actuated by fluid pressure, but it will be understood that any convenient arrangement may be employed for applyin an actuating force to lever l5. With the arrangement 'of parts shown, it will be apparent that a very slight movement of the pressure memher in a vertical direction resultsin a very considerable movement of the spring II in a vertical direction due to the arrangement of fulcrums and hence the multiplying action-of the levers I5 and I3.

In order to cause the levers'l3 and I 5, and hence the contacts, to follow recession of the pressure member I8. a pair of spring I9 and 20 are mounted'to exert a force upon the lever I3 tending to rotate the same in a counterclockwise direction about its pivot II. The provisionof two springs, as shown, facilitates calibration of the switch within very narrow limits of tolerance, a rough calibration being accomplished by adjustment of a relatively heavy spring I9 arranged to exert its force through a relatively short moment arm and the line calibration being accomplished 3 by appropriate adjustment or a relatively weak spring}. arranged to exert iis force through a greater moment arm.

If it be desired to provide the switch with a mechanism for positively moving the contact member I in the event that the contacts should stick and the impositive connections through spring II and link 8 be incapableof moving the contacts, the contact member I may have an extension 2I beyond the knife-edge 2. The extremity of the extension 2|v is embraced by.a stirrup 22, but these parts are normally not in physical engagement one with the other. As shown in the drawings, the stirrup 22 is mounted upon an insulation plate 22 fixed to lever I3 so that the stirrup moves in a verfical direction as the lever I3 rocks about its pivot ll. when, in the event the contacts have stuck, the spring II yields and does not accomplish a movement of the contact member inresponse to movement of lever I3, one side or the other of stirrup 22 will come into engagement with the extension 2| of contact member I and directly transmit aforce from lever I3 thereto, positively moving the same.

It will be understood, of course, that, in situations where such sticking of the contacts is not likely to occur, the extension 2! and the stirrup 22 may be omitted.

An understanding of the operation and advantages of the structure will be clear from a consideration of Figures 3 to 6, inclusive, wherein the several parts are diagrammatically shown. In Figure 3, the contact member I is at one extreme position wherein the movable contact is engaging the stationary contact "I- When in this position, the force exerted by spring ii throughv link 8 tends to maintain the knife-edge 2 seated, but the direction of the force imparted to contact member I through link 8 is such as to'bias the contact member in a clockwise direction about its fulcrum at 2. If, now, a force be exerted such as to rock lever I3 about its pivot It, the spring II moves upwardly to the position shown in Figure 4 wherein it will be observed that the direction in which the force of spring II is imparted through link 3 to contact member I passes through the fulcrum 2, asshown by the broken line, but atthis time the contacts 5 are still in engagement with the upper stationary contact 1. Any slight movement beyond the position shown. in Figure 4 causes the line of force from spring II to contact member i to pass on the lower side of the fulcrum at 2 and consequently swings the contact member into the position shown in Figure 5 where the movable contacts 5 engage stationary contacts 6. In the event, however, that the movable contact 5 has stuck in engagement with the stationary contact I, the contact'member I may remain in the position shown in Figure 4 even after the position of link 8 has shifted so that the line of force is be-' low the fulcrum at 2; Such condition is represented in Figure 6 where it will be observed that,

although the line of force from spring II is in a that, at the stage illustrated in Figure 6, the force of spring II tends to assist the breaking of the contacts 5 and I and consequently, when the stirrup 22 has applied sufllcient force to break the frozen connection, the force of spring II comes into play to immediately snap the contact member to'its opposite position, as shown in Figure 5. If movable contact 5 should freeze to stationary contact 6, the operation of the parts is in the reverse order. In this instance, the upper lip of stirrup 22 engages extension 2| to free the contact member I for movement in a. clockwise direction about its fulcrum 2 under the influence oi. spring II.

From the construction and organization of the parts, as above described, it will be apparent that, if it be desired to replace contact member I, all that is necessary is to bias spring II leftwardly until link 8 is released either from the spring or lip Ill of contact member I whereupon the contact member may be lifted out of position without necessitating the removal of any shafts or other balancing devices. This aspect of the invention is important not only from the standpoint of replaceability of the contact member, but also in that itgreatlyfacilitates the initial formation and assembly of the parts.

From the foregoing description, those skilled in the art should readily understand the operation and advantages of, the switch. While one complete embodiment has been described in detail, it is not intended that the invention be considered as limited to the details of that disclosure, but, on the contrary, it is realized that many modifications will suggest themselves to those skilled in the art without departing from the spirit of the invention or the scope of the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Pat- I cut is:

l. A pressure switch comprising a contact carrier movable between two positions, means .for imparting moving force to said carrier, said means including a spring continuously biasing the carrier in a direction substantially perpendicular to,

the direction of movement of said carrier, a thrust link interconnecting said spring and said carrier, said spring being movable in a direction substantially parallel to the direction of movement rier movable between two positions, means for imparting moving force to said carrier, said means including a spring continuously biasing the car- "rier in a direction substantially perpendicular to the direction of movement of said carrier, a thrust link interconnecting said spring and said carrier, said spring being movable in a direction substantially parallel to the direction of movebetween said spring and said carrier and the connection between said carrier and said mounting being freely separable upon movement in the direction opposed by the force of said spring, and means for changing the direction of the moment of the spring upon the carrier to move the latter between said two positions.

4. A pressure switch having a contact carrier movable between two positions about a fulcrum, a knife-edge mounting providing the fulcrum for said carrier, a thrust link engaging a part of said carrier remote from its fulcrum, and a movable spring urging said link into engagement with said carrier and said carrier into seating relation at said knife-edge pivot, the connections between said spring said link and said carrier, as well as the connections between said carrier and said mounting, being freely separable upon movement in the direction opposed by the force of said spring.

5. A pressure switch having a contact carrier movable between two positions about a fulcrum, a knife-edge mounting providing the fulcrum for said carrier, a thrust link engaging a part of said carrier remote from its fulcrum, a movable spring urging said link into engagement with said carrier and said carrier into seating relation at said knife-edge pivot, said spring being the only means preventing displacement of said carrier from said mounting, and a movement-multiplying leverage supporting said spring.

6. A pressure switch having a contact carrier movable between two positions about a fulcrum, an operating lever pivoted at one end, an actuator engaging said lever closely adjacent the pivoted end, a spring mounted on said lever at the 0pposite end thereof, the pivot for said lever and the fulcrum for said contact carrier lying in substantially parallel planes and said spring being tensioned to exert its force in-a direction substantially parallel with the planes thereof, and a link transmitting the force of said spring to said,

carrier and arranged to reverse the moment thereof during movement of said lever.

'7. A pressure switch having a contact carrier movable between two positions about a fulcrum,

an operating lever pivoted at one end, an actuator engaging said lever closely adjacent the pivoted end, a spring mounted on said lever at the opposite end thereof, the pivot for said lever and the fulcrum for said carrier lying in substantially parallel planes and said spring being tensioned to exert its force in a direction substantially parallel with the planes thereof, a link transmitting the force of said spring to said carrier and arranged to reverse the moment thereof during movement of said lever, and a part movable with said lever embracing but normally not engaging said carrier on the opposite side of the fulcrum thereof from said link.

8. A pressure switch having a contact carrier movable between two positions about a fulcrum, an operating lever pivoted at one end, a spring mounted on said lever at the opposite end thereof, the pivot for'said lever and-the fulcrum for said carrier lying in substantially parallel planes and said spring being tensioned to exert its force in a direction substantially parallel wih the planes thereof, a link transmitting the 'force of said spring to said carrier and arranged to reverse the moment thereof during movement of said lever, an actuating lever pivoted remote from the pivot of the operating lever but engaging the latter adjacent its pivot point, and means for applying a force to the acuating lever between its pivot and its point of engagement with said operating lever.

LAWRENCE M. PERSONS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS 

